This invention relates generally to the field of mattresses, and in particular to so called one-sided or no-flip mattresses. More specifically, the invention relates to such mattresses that are constructed using an inner core of springs.
Spring mattresses have been in use for over 100 years. Existing spring mattresses use a variety of spring types to form their inner core. Perhaps the most common is the traditional wire spring assembly having a set of interconnected wire spring coils. As is well known in the art, a major supplier of such springs is Leggette and Platt.
Another type of spring assembly is the so-called Marshall construction that was developed in the late 1890""s by Marshall Mattress of Toronto, Canada. The Marshall design utilizes fabric pockets to encapsulate each spring. In this way, the coils may flex separately from each other. Examples of such pocket coil spring designs are described in, for example, U.S. Pat. Nos. 685,160; 4,234,983; 4,854,023; 6,029,957; and 6,295,676 and published PCT No. WO99/32396, among others. The complete disclosures of all these references are herein incorporated by reference.
Traditional mattresses have a padding layer disposed both on top of and beneath the core of springs. This is encased within a fabric or ticking, and may optionally include additional layers of padding to form a xe2x80x9cpillow topxe2x80x9d mattress as is known in the art. Because of potential uneven wear during the life of the mattress, many manufacturers recommend periodically rotating or flipping the mattress. However, because this can be difficult and inconvenient, many users do not follow this practice. For those that do, this exercise can be annoying.
As a result, the one-sided or no-flip mattress has been developed. Several manufacturers have developed and sold such mattresses at least as early as the mid 1990s. For instance, Sleep Therapy mattresses have been sold by Wickline Bedding Co., San Diego, Calif. since the early 1990s. These mattresses have a polyurethane foam layer underneath the springs and a traditional padding layer on top. This design was subsequently adopted by Simmons Company as demonstrated by their U.S. Pat. No. 6,243,900, the complete disclosure of which is herein incorporated by reference.
This invention is related to improved methods for manufacturing so called one-sided or no-flip mattresses. As described hereinafter, such mattresses provide increased firmness, stability and comfort, among other features. Further, such mattresses may be economically produced to provide a commercially attractive mattress.
The invention provides exemplary mattresses as well as methods for their construction. In one embodiment, a mattress comprises a core of springs having a fabric covering. For example, the springs may be individually encased in fabric pockets. A top padding layer is positioned on top of the core of springs, and a bottom support layer is disposed below the core of springs. The bottom support layer is bonded to the fabric covering of the core to couple the bottom support layer to the core of springs. Such a construction is particularly useful where at least some of the fabric pockets are pre-joined to each other near midpoints of the coils so that independent movement of both the tops and bottoms of the coils is permitted. By bonding the bottom support layer to the fabric covering, additional stability is provided to the mattress by limiting the lateral movement of the bottoms of the springs relative to each other while still permitting individual movement of the tops of the springs relative to each other.
Another feature of such mattresses is that the bottom support layer may be constructed of a matrix of foam elements, such as a rebond material. Such materials are relatively dense, have good firmness, and are still cost effective. For example, the bottom support layer may have a density of about 3 pounds per cubic foot or greater, with one particularly useful density being about 3.5 to about 4.5 pounds per cubic foot. The firmness of the bottom support layer may be measured in terms of its mean indentation force deflection (IFD) that may be in the range from about 40 to about 80, and more preferably from about 50 to about 70. Further, the bottom support layer may have a thickness in the range from about 0.5 inches to about 3 inches and may be formed from one or more stacked pieces.
In one aspect, a border element, such as a border wire, may be coupled to a perimeter of the core of springs. For example, the border wire may be clipped to the individual coils with rings. In some cases, a border wire may not be included. In one alternative, a foam encasement may be used to replace one or more of the outside rows of springs so that a border wire is not needed.
In another aspect, a quilted material may be placed over the top layer, and a border material may be secured about the sides of the mattress. A cover material may also be placed over the bottom support layer.
To manufacture such a mattress, the bottom support layer is bonded to the fabric pockets using a bonding material, such as glue. The top padding layer is placed on top of the core of springs and a quilted or other material is placed over the core and top and bottom layers.